Neurotransmitters are stored in synaptic vesicles so that their release may be regulated by neural activity. For classical neurotransmitters, vesicular storage requires transport from the cytoplasm, where many of the transmitters are synthesized. However, little is known about neurotransmitter transport into synaptic vesicles or its potential for regulation, which would affect quantal size and hence the efficacy of synaptic transmission. The long-term objectives of this proposal are to understand how the transport of neurotransmitters into synaptic vesicles influences the processing of neural information and contributes to human disease. The proposal focuses on the vesicular transport of biogenic amines because these transmitters are involved in major mental illnesses and Parkinson's disease. The strategy is to isolate cDNA clones for the vesicular transport proteins, reconstitute their activity in a heterologous system and use this system to characterize the structural basis for transport function and regulation. We have recently isolated a cDNA clone for the chromaffin granule amine transporter using selection in the neurotoxin MPP+. The first specific aim of the proposal is to generate antibodies to this transporter and use these to confirm its suspected intracellular location. The second aim is to isolate related cDNAs and use the pattern of expression to suggest their function. The third specific aim is to characterize the functional properties of the transporters expressed in a heterologous system. Mutant and chimeric proteins will be used to dissect the structural basis for transport activity, specificity and interaction with pharmacologic agents. Heterologous expression in a neural cell line will identify the potential for regulation. Correlation of the molecular analysis with biological models and genetic information can then be used to determine the role of vesicular neurotransmitter transport in information processing and neuropsychiatric disease.